Applied Design

For being eager to take the first steps to make our project real, we designed a physcial unit applied in the field to purify farmland runoff water (regarded as the main factor of agricultral pollution^[1]) including 3-PBA and pyrethroids.

Through farmland investigation, we found runoff water from cropland was seldom collected and purified. Based on our questionnaire, about 10% of interviewees come from rural areas, but only 3.5% of the whole interviewees know that pyrethroids are widely used pesticides in agricultural production and its harm to ecology, so that most people in rural areas lack the awareness of pesticide pollution in agriculture. Based on documents, we found 1) people had no idea about farmland runoff water disposal ^[2]. 2) people in the research institutes always want to use plant ryegrass and photinia fraseri to lighten contamination^[3]. 3) The ponds can collect the contaminant ^[4].

To put the engineered bacteria into practice, some issues have to be handled.

• Pyrethroids biodegradation in the unit
• Meeting the standard of farmland discharge in China main land
• Real situation usage imagination

Pyrethroids biodegradation in the unit

3-PBA comes from its parent compounds pyrethroids which are more frequently touched by the public and also is used as a generic biomarker for multiple pyrethroids exposure for pyrethroid residues in the environment. Both 3-PBA and pyrethroids can be found in the run off water. Sphingobium wenxiniae JZ-1 was designed to put into the unit to degrade pyrethroids.

Meeting the standard of farmland discharge in China main land

• pH=5.5～8.5
• BOD < 80～100 mg/L
• COD < 100～200 mg/L
• SS < 90～150 mg/L
• Fecal Escherichia coli < 10000 per liter
• Number of ascaris eggs < 2 per liter

According to the urban sewage treatment method , sedimentation , sludge treatment , disinfecton^[5] can cut down the index value to meet the standard.

*The whole unit is divided into five rooms and they are numbered separately (the second room is under the first room; number 5 is not marked and the fifth room is near the fourth room from right to left orientation ) and all the plates used to separate the unit into five rooms are covered by the 0.22μm bacterial membrane to prevent the bacterial escape.

On the bottom of the first room there is acticarbon to pretreat the water to be purified. The second room is used to degrade pyrethroids applying Sphingobium wenxiniae JZ-1. The third room is used to cut down the BOD and COD index value applying yeast and Actinobacillus. The forth room is used to degrade 3-PBA applying the engineered bacteria. The fifth room is used to sterilize together with flocculant to sludge. All the microbe referred can be fed up by semisolid culture-medium^[6,7]. The unit is pumped.

Click to download the powerpoint to see the working process.

Real situation usage imagination

The physical unit will be put into the places applied pyrethroids to achieve its value. Set a man-made pond(①) to collect pyrethroids and 3-PBA and the physical unit(②) is beside the pond. Between the pond and the place applied pyrethroids(③) there is a moderate climb(④) to help the pyrethroids and 3-PBA collecting. Avoiding to pollute the drinking water source the man-made pond should be at least away from the water source 90 meters.

Reference